Control method and system for use when growing thin-films on semiconductor-based materials

ABSTRACT

A process and system for use during the growth of a thin film upon the surface of a substrate by exposing the substrate surface to vaporized material in a high vacuum (HV) facility involves the directing of an electron beam generally toward the surface of the substrate as the substrate is exposed to vaporized material so that electrons are diffracted from the substrate surface by the beam and the monitoring of the pattern of electrons diffracted from the substrate surface as vaporized material settles upon the substrate surface. When the monitored pattern achieves a condition indicative of the desired condition of the thin film being grown upon the substrate, the exposure of the substrate to the vaporized materials is shut off or otherwise adjusted. To facilitate the adjustment of the crystallographic orientation of the film relative to the electron beam, the system includes a mechanism for altering the orientation of the surface of the substrate relative to the electron beam.

This invention was made with Government support under Contract No.DE-AC05-960R22464 awarded by the U.S. Department of Energy to LockheedMartin Energy Research Corporation, and the Government has certainrights in the invention.

BACKGROUND OF THE INVENTION

This invention relates generally to the growth of thin-films uponsemiconductor-based materials and relates, more particularly, to themeans and methods by which the growth of such thin-films in a highvacuum facility can be controlled.

The growth of thin-films in a high vacuum facility may be monitored withReflection High Energy Electron Diffraction (RHEED) techniques involvingthe use of a high energy electron beam emitted from an electron gun todiffract electrons off of a substrate (i.e. target) surface at aglancing angle. These diffracted electrons are diffracted in a patternwhich provides crystallographic information of the film surface. Morespecifically, each crystallographic condition of the film surfaceevidences a signature electron diffraction pattern so that during athin-film growth process, a desired crystallographic condition of thefilm surface can be substantiated by an electron diffraction patternwhich is indicative of the desired crystallographic condition.

However, to obtain desired RHEED measurements by conventionaltechniques, the substrate upon which the thin film is grown is rigidlymounted within the high vacuum facility and must typically, on occasion,be physically adjusted in position relative to the electron gun. Ofcourse, in order to make adjustments in the position of the substrate,the film growth process must be halted and the facility may even have tobe opened to gain access to the substrate. It follows that thisconventional technique is time-consuming and is not well-suited for massproduction techniques.

An object of the present invention is to provide a new and improvedprocess and system for use during the growth of thin-films upon asubstrate surface in a HV facility enabling the film growth process tobe efficiently controlled.

Another object of the present invention is to provide such a processwhich is well-suited for mass production techniques.

Still another object of the present invention is to provide such aprocess which is uncomplicated to perform yet effective in operation.

SUMMARY OF THE INVENTION

This invention resides in a process for growing a thin film upon thesurface of a substrate involving the exposure of the substrate surfaceto vaporized material in a high vacuum (HV) facility and an associatedsystem.

Within the process of the invention, the improvement comprises the stepsof directing an electron beam generally toward the surface of thesubstrate as the substrate is exposed to vaporized material so thatelectrons are diffracted from the substrate surface by the beam andmonitoring the pattern of electrons diffracted from the substratesurface as vaporized material settles upon the substrate surface. Theimprovement further includes the step of shutting off or otherwiseadjusting the exposure of the substrate to the vaporized materials whenthe monitored pattern achieves a condition indicative of the desiredcondition of the thin film being grown upon the substrate.

A system of the invention includes means mounted within the HV facilityfor directing an electron beam generally toward the surface of thesubstrate so that electrons are diffracted from the substrate surfaceand means mounted within the HV facility for monitoring the pattern ofelectrons diffracted from the substrate surface. The system alsoincludes means connected between the substrate and the directing meansfor moving the substrate and the directing means relative to one anotherto facilitate an adjustment of the crystallographic orientation of thethin film being grown upon the substrate surface relative to thedirected electron beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a fragment of an ultra highvacuum (UHV) facility, shown partially cut-away, within which anembodiment of a growth-control system of the present invent employed.

FIG. 2 is a longitudinal cross sectional view of a portion of the UHVfacility of FIG. 1.

FIG. 3 is a cross-sectional view taken about along line 3—3 of FIG. 2.

FIG. 4 is a view illustrating in block diagram form the operation of theembodiment of the system utilized in the FIG. 1 system.

FIGS. 5 and 6 are photographs providing Reflection High Energy ElectronDiffraction (RHEED) data collected at various stages of BaSi₂ formationon the (001) surface of silicon.

FIGS. 7-9 are photographs providing RHEED data collected at variousstages of a build up of a perovskite onto a substrate surface.

FIG. 10 is a perspective view of a support plate capable of beingmounted within the growth facility of FIG. 1 and a plurality ofsubstrates which have been mounted upon the plate.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Turning now to the drawings in greater detail, there is illustrated inFIG. 1 a schematic representation of thin-film growth equipment 20within which an embodiment of a growth-control system, generallyindicated 22, is incorporated. The equipment 20 includes an ultra-highvacuum (UHV) facility 24 having a container 26 defining an inner chamberwithin which a substrate 28 is positionable and a plurality of canisters30 mounted within the base of the container 26 for providing a vaporsource of metals desired to be added to the substrate 28 in the form ofa deposited film. As will be described in greater detail herein, thesystem 22 facilitates the monitoring of the condition of the crystallinelattice of the film being grown upon the surface of the substrate 28 sothat better control over the growth of the film can be had.

As will be appreciated by those skilled in the art, when preparing theUHV facility 24 to grow a film of desired composition upon a substrate28, the substrate 28 is mounted within the chamber of the facilitycontainer 26 so that its surface, indicated 32 in FIG. 2, facesgenerally downwardly, and each element desired to be deposited upon thesubstrate surface 32 is placed within a corresponding canister 30. Inthis connection, each canister 30 is adapted to hold a cruciblecontaining a desired element and contains heating elements forvaporizing the metal. An opening is provided in the top of each canister30, and a shutter 31 is associated with the canister opening formovement between a closed condition at which the contents of thecanister 30 therein is isolated from the substrate surface 32 and anopened condition at which the contents of the canister 30, i.e. thevaporized element, is exposed to the substrate surface. In addition, anoxygen source 34 is connected to the chamber of the facility 24 so thatby opening and closing a valve 38 associated with the source 34, oxygencan be delivered to or shut off from the chamber. The opening andclosing of each canister shutter 31 and the oxygen source valve 38 isaccurately controlled by a computer controller 36.

For purposes of monitoring the condition of the film being grown uponthe substrate surface 32, the system 22 includes an electrongun/detector assembly 40 mounted alongside the substrate 28 adjacent thetop of the facility container 26. More specifically, the electrongun/detector assembly 40 includes an electron gun 42 and a detector 44mounted at diametrically-opposed locations across the substrate surface32 and is used to monitor the condition of the film being grown by knownReflection High Energy Electron Diffraction (RHEED) techniques. Briefly,the electron gun 42 directs a high energy electron beam generally toward(albeit at an angle) to diffract electrons off of the substrate surfaceat a glancing angle. The diffraction pattern of the electrons isdetected by the detector 44, such as a fluorescent screen, and thisdiffraction pattern provides crystallographic information relating tothe condition of the film surface.

The information desired by the RHEED techniques described herein relatesto the lateral arrangement of the atoms in the topmost layer(s) of thefilm being built. Although a detailed description will not be providedherein as to how to interpret RHEED patterns, suffice it to say that theRHEED pattern is essentially the reciprocal lattice of the surface.

It is also fundamental to the monitoring process performed with theelectron gun/detector assembly 40 that the desired arrangement of atomsat (or near) the surface of the substrate will provide a specificsignature in its RHEED pattern. Along the same lines, it will also beappreciated that as the atoms of vaporized material settle upon (andthereby build up upon) the surface of the substrate 28, changes areexperienced in the crystallographic characteristics of the substratesurface 32. Accordingly, the RHEED patterns acquired from the substratesurface 32 at one stage of a vapor-deposition process are different fromthe RHEED patterns acquired from the substrate surface 32 at asubsequent stage of a film-growth process. It also follows, therefore,that when the RHEED pattern matches the signature characteristiccorresponding to the desired condition of the substrate surface 32, thenthe thin film will have attained its desired quality or condition.

To obtain accurate characterizations of the substrate surface 32 duringa film-growth process, it occasionally becomes necessary to alter theorientation of the substrate 28 relative to the gun/detector assembly 40(and consequently the electron beam directed from the gun 42 thereof) sothat the gun-directed beam is directed along a desired path (e.g. an[001] direction) across the crystalline lattice of the substrate surface32. Heretofore, adjustments between the relative position of thesubstrate surface 32 and the gun/detector assembly 40 required that thefilm-growth process be halted (by, for example, shutting off theexposure of the substrate surface 28 to the vaporized material) and thegrowth facility 24 opened to gain access to the substrate 28 foradjustment of its position. Of course, after the positional adjustmentis made to the substrate 28, the facility 24 is closed, and the highvacuum conditions must be re-established before the growth process canbe re-initiated. It follows that prior art efforts required to make apositional adjustment of the substrate relative to the gun/detectorassembly were laborious and time-consuming.

It is a feature of the system 22 that it includes means, generallyindicated 50, for expeditiously altering the relative position betweenthe substrate surface 32 and the gun/detector assembly 40 during thecourse of a thin film deposition process to thereby facilitate anadjustment in the orientation of the gun-emitted beam relative to thesubstrate surface 32. The depicted altering system 50 includes means 52for rotating the substrate 28 about its vertical centerline, indicated54 in FIG. 2, to thereby alter the angular relationship of thegun-emitted beam relative to the crystalline lattice structure of thesubstrate surface 32. The capacity to adjust the angular relationship ofthe gun-emitted beam in this manner permits the gun-emitted beam to beaccurately aligned along a predetermined direction (e.g. an [001]direction) across the crystalline lattice of the substrate surface 32 inorder to obtain the desired characteristics of the lattice of the filmbeing grown upon the surface of the substrate 28.

In the depicted example, the altering means 50 includes a rotatableturntable 56 mounted for rotation about the vertical axis 54, which axiscorresponds with the vertical centerline of the substrate surface 28,and the electron gun 42 and detector 44 are supported from the uppersurface of the facility 24 so as to be disposed at diametrically-opposedlocations across the turntable 56. The turntable 56 is plate-like inform and is supported at the end of a shaft of a servomotor 58 which is,in turn, supported from the upper surface of the facility 24. When it isdesired to alter the positional relationship of the substrate surface 32relative to the gun/detector assembly 40, appropriate command signalsare sent to the motor 58 from the computer controller 36 to rotate theturntable 56 by a desired amount. RHEED measurements can then beobtained from the substrate surface 32 at that altered positionalrelationship.

Each of the electron gun 42 and detector 44 of the gun/detector assembly40 is supported from the chamber of the facility 24 in a manner which iswell-known in the art. Briefly, each of the gun 42 and detector 44 issupported in a fixed position at the lower end of a correspondingbracket 60 or 62 which is attached at its upper end to the top of thefacility chamber. As do other conventional electron guns, the depictedgun 42 includes internal mechanisms which permit the direction of theemitted electron beam to be altered along a vertical plane to therebyalter the angle of incidence between the gun-emitted beam and thesubstrate surface 32. It follows that by rotating the substrate 28 aboutits centerline 54 and adjusting, as necessary, the direction of theemitted beam along a vertical plane, RHEED measurements can be takenfrom any direction across any location on the surface 32.

It will also be understood from the foregoing that in order to obtain adesired RHEED measurement of the substrate surface 32 (and therebyaccurately monitor the condition of the crystalline lattice of thesurface 32), it may be required that the angular relationship betweenthe gun/detector assembly 40 and the substrate surface 32 about thevertical axis 54 and/or the angle of incidence between the gun-emittedbeam and the substrate surface 32 be altered. If such is the case, theservomotor 58 is appropriately energized to reposition the substrate 28about the axis 54 to reorient the crystallographic orientation of thesubstrate 28 relative to the gun/detector assembly 40 or the internalmechanisms of the gun 42 are actuated to adjust the angle of incidenceof the gun-emitted beam relative to the substrate surface 32.

As mentioned above, the servomotor 58 (as well as the internaladjustment mechanisms of the gun 42) are connected to the controlcomputer 36 for accurately controlling the positional relationship ofthe gun/detector assembly 40 relative to the crystalline lattice of thesubstrate surface 32. In other words, the control computer 36 isresponsible for sending command signals to the motor 58 and gun 42which, in turn, are responsible for positioning the lattice structure ofthe surface 32 in a desired orientation relative to the gun-emitted beamand for directing the gun-emitting beam toward the substrate surface 32at a desired angle of incidence.

The operation of the system 22 can be summarized with reference to theblock diagram shown in FIG. 4. During a deposition process, one or moreshutters 31 (FIG. 1) and/or the valve 38 from the oxygen source 34 areopened to expose the substrate surface 32 to vaporized materials emittedfrom the canisters 30 and/or to oxygen from the source 34. Meanwhile,the electron gun 42 and detector 44 are used to diffract electrons fromthe substrate surface 28 in a RHEED-monitoring operation as thedeposition-process is underway. The position of the electron gun anddetector relative to the substrate surface may have to be altered, asnecessary, in order to obtain the desired measurements (i.e. the desiredcrystallographic orientation of the electron beam relative to thesurface 32). To adjust the positional relationship of the gun-emittedbeam relative to the substrate surface 32 (and thereby adjust the eitheror both of the angular relationship of the gun/detector assembly 40about the vertical axis 54 and the angle of incidence between thegun-emitted beam and the substrate surface 32), the control computer 36sends appropriate command signals to the servomotor 56 and the internaladjustment mechanisms of the gun 42.

Within the database of the control computer 36, there is includedprogrammed information as to how the diffraction pattern of theelectrons should appear when the crystallographic information of thesubstrate surface has attained its desired characteristics. During afilm-deposition process, monitoring circuits 72 (FIG. 4) within thecomputer 36 gather the RHEED information being collected by thegun/deflector assembly 40 and comparison circuits 70 continually comparethe gathered RHEED information to the stored information. When the RHEEDdata being collected matches the crystallographic information stored inthe computer 36 as a target pattern, which information, or pattern, isindicative of a desired condition of the thin film being grown upon thesubstrate 32, appropriate command signals (initiated at a shuttercontrol circuit 74 are sent to the canisters 30 for closing the shutters31. When it becomes necessary to adjust the positional relationship ofthe lattice structure of the substrate surface 32 relative to thegun-emitted beam, appropriate command signals (originating from anadjustment circuit 76) are sent to the servomotor 58 or the gun 42. Aswill be apparent in the following examples, the shutters 31 can be shutoff upon completion of a single film layer of a desired material or canbe shut off upon completion of a fraction of a monolayer of a desiredmaterial. Of course, upon completion of a build-up of a single filmlayer of a desired material, the build-up of an additional layer of asecond desired material can be initiated by opening (by way ofappropriate command signals from the computer 36) the shutters 31 to thecanisters 30 within which the materials (or the constituents thereof)are emitted.

EXAMPLE #1

In a first example (which is applicable to the build up of an alkalineearth oxide upon a semiconductor-based substrate comprised of silicon,germanium or a silicon-germanium alloy), the system 22 will be describedherein in conjunction with the build up of an epitaxial layer of thealkaline earth oxide BaO upon a silicon substrate. The principles of thegrowth process are described in detail in U.S. Pat. No. 5,225,031, butfor present purposes are summarized here as follows.

A silicon substrate 28 having a surface 32 which is atomically clean ismounted within the HV facility 24 so that its surface faces generallydownwardly, and then the temperature of the substrate is raised to anelevated temperature of between about 850° and 1050° C. as high vacuumconditions are developed within the facility 24. The shutter 31 coveringone flux source (i.e. one canister 30) of the metal Ba is opened so thatthe metal Ba is deposited upon the substrate surface until a fraction ofa monolayer (i.e. one-fourth of a monolayer) of the metal covers thesilicon substrate 32. At that point, the deposition process is halted,and the temperature of the substrate is lowered to between about 200°and 300° C.

Once the lower substrate temperature is reached, an additional amount ofthe metal Ba is deposited upon the substrate from the flux source untilthe substrate 32 is covered by about one monolayer of the metal. Thepressure of the HV facility 24 is then raised to a target pressure(between about 1×10⁻⁶ torr and 5×10⁻⁶ torr), and then the substratesurface 32 is exposed to oxygen and an additional amount of the metal Bafrom the flux source so that the epitaxial oxide BaO begins to grow uponthe substrate surface 32.

Hence, it follows that during a first growth stage of this exampleinvolving an initial deposition of Ba upon the silicon substrate, it isimportant that the deposition process be halted when a fraction (i.e.one-fourth) of a monolayer of the Ba layer is reached. Similarly, itfollows that during a second stage of this growth process involving thesubsequent deposition of Ba upon the silicon substrate, it is importantthat the deposition process be halted when the thickness of the thinfilm of Ba reaches about one monolayer in thickness.

Turning attention to the function of the system 22 during the buildingof the aforedescribed layer of BaO upon a silicon surface, a siliconsubstrate having an atomically-clean surface is mounted face-downwardlyupon the turntable 56. The temperature of the substrate is then raisedto the aforedescribed elevated temperature, and high vacuum conditionsare developed within the facility. The metal Ba from a flux source ofthe metal (contained within one of the canisters 30) is then begun to bedeposited upon the substrate surface while the conditions of thedeposited film are monitored with the electron gun/detector assembly 40.In other words, as the flux of Ba begins to settle upon the siliconsurface, the lateral spacing of the Ba atoms are monitored with theelectron gun/detector assembly 40 and the Ba deposition (of this firstphase of the growth process) is halted when the pattern of diffractedelectrons, as detected by the detector 44, obtains a conditionindicative of one-fourth of a monolayer of Ba. To this end, the computer36 contains information relating to the signature RHEED patternindicative of the growth of one-fourth of a monolayer of Ba.

For comparison purposes, there is shown in FIG. 5 the RHEED pattern ofthe diffracted electrons when one-sixth of a monolayer of Ba isdeposited over the silicon substrate, and there is shown in FIG. 6 theRHEED pattern of the diffracted electrons when one-fourth of a monolayerof Ba is deposited over the silicon substrate. It can be seen that theenergy of the electrons (corresponding generally to the brightness ofthe dots in the pattern) is greater in the FIG. 6 pattern at the 1/2,0location than it is in the FIG. 5 pattern whereas the energy of thediffracted electrons is less in the FIG. 6 pattern at the 1/3,0 locationthan it is in the FIG. 5 pattern.

It therefore follows that when the pattern of diffracted electronsobtained across the substrate surface being monitored attains thepattern depicted in FIG. 6, the Ba deposition is halted (by closing theappropriate canister shutter 31) and the temperature of the substrate islowered and the internal pressure of the facility is adjusted asaforedescribed. When Ba deposition is subsequently resumed (to initiatethe second stage of the Ba deposition), the film surface is againmonitored with the electron gun/detector assembly 40 to determine whenthe thickness of the Ba layer reaches one monolayer. Again, the patternof the diffracted electrons gathered by the gun/detector assembly 40bears a RHEED pattern indicative of the signature RHEED pattern of asingle monolayer thickness of Ba, the deposition process is halted byclosing the appropriate canister shutter 31.

EXAMPLE #2

In a second example [which is applicable to the growth of a thin filmdesignated generally as A′BO₃(as described in our U.S. Pat. No.5,830,270) upon an AO or BO₂ truncated perovskite surface wherein eachunit cell of the A′BO₃ structure is comprised of a single plane ofalkaline earth oxide (AeO) and a single plane of a transition metaloxide (TmO)], the system 22 will be described herein for use inconjunction with the build up of a perovskite oxide structure, such asBaTiO₃, upon an alkaline earth oxide, exemplified by an MgO, surface.The principles of such a growth process is described in detail in U.S.Pat. No. 5,693,140 so that a detailed description of the build-upprocess is not believed to be necessary. It is relevant in the build-upprocess, however, that the perovskite structural unit for BaTiO₃ iscomprised of separately-identifiable planes wherein one plane iscomprised of BaO and the other plane is comprised of TiO₂. The build-upprocess is effected by depositing an initial plane of TiO₂ upon the MgOsurface, and thereafter depositing alternating planes of BaO and TiO₂upon the initial plane.

The two planes (i.e. the BaO and Tio₂ planes) of the perovskite BaTiO₃contain different atoms with different atomic scattering factors and aresensitive to observation by electron scattering from a film surface thatmight be truncated with either a BaO plane or a TiO₂ plane. Generally,within a perovskite structure, the BaO plane is considered as thealkaline earth oxide (AeO) plane and the TiO₂ plane is the transitionmetal oxide (TmO) plane of the perovskite structure.

The system 22 of the present invention is used to monitor the surfaceupon which the vaporized materials are being deposited to determine whenovercoverage (or atomic concentration) of the corresponding planes ofAeO or TmO occurs. In other words, since a growing film which istruncated with either an AeO plane or a TmO plane can be characterizedwith RHEED to determine its composition, RHEED data collected during themonitoring of the deposition surface can be used to determine when agrown plane of AeO or TmO has ben completed.

For example, there is shown in FIGS. 7-9 show RHEED images taken fromCaTiO₃ showing reconstruction rods visible at the [100] and [210] zoneaxes for a titanium-rich TiO₂truncation and at the [110] zone axis for aCa rich CaO-truncation. Characteristically in these images are brighterprominent diffraction rods (vertical streaks) and dimmer “½ order”diffraction rods in between the principal or brighter diffraction rods.For a surface, either AeO or TmO-truncated, that is stoichiometric, the½ order rods do not show up. These ½ order rods are the signature ofovercoverage that are monitored in real time during thin film growth.

Although the RHEED images of FIGS. 7-9 indicate Ti-rich (FIGS. 7 and 9)and AeO-rich (FIG. 8) deposits indicative of an overcoverage of theperfect stoichiometric conditions of the layer being deposited,adjustments can be made to the deposition process by, for example,shuttering or dynamically changing the arrival rate of the constituentshown to be in excess. In other words, even though the signature patternof constituent overcoverage appears (as in FIG. 7, 8 or 9), appropriateadjustments can be made in the deposition process so that the ½ orderrods disappear and the diffraction condition of the perfectlystoichiometric perovskite is again obtained.

By capturing these RHEED images (e.g. FIGS. 7-9) in real time using adigitization of a video image taken from the phosphor screen that iscollecting scattered electrons from the growing thin film surface,computer analysis of line scans across the major and minor rods fromthese patterns are used as feedback for a composition control process ina UHV growth chamber. This control process can be as simple as handcontrol of system growth parameters by an operator or more elegantlyimplemented in an electronic control process. Based upon testingperformed to date, a sensitivity of at least 0.07 monolayers can be had.Heretofore, such a sensitivity was not attainable by any other knowndynamic growth process monitoring scheme.

It follows from the foregoing that a system has been described whichmonitors the crystallographic characteristics of the last-grown planeand permits plane-by-plane composition adjustment and/or termination ofthe growth process based upon the monitored characteristics.

It will be understood that numerous modifications and substitutions canbe had with the aforedescribed embodiments without departing from thespirit of the invention. For example, although the aforedescribedprocess has addressed the use of electron beam diffraction formonitoring the surface characteristics of the film being grown,alternative diffraction techniques, such as x-ray diffraction, which aresufficiently sensitive to atomic surface structure can be used. However,for x-rays, the sensitivity to a crystal surface is complicated by thebeam penetration in normal x-ray methods. However, in a synchrotron inwhich the x-ray beam is extremely intense and can be made to besurface-sensitive, the x-ray methods equally can be used to monitor thesurface conditions.

Further still, although a single substrate 28 has been shown anddescribed as being positioned within the facility 24 of the FIG. 1system 22 for a thin film deposition operation as the thin film growthupon the substrate 28 is monitored in accordance with the process of thepresent invention, it will be understood that more than one substratecan be mounted within the facility 24 of the system 22 during a thinfilm deposition operation so that a thin film is deposited upon eachsubstrate mounted within the facility 24. For example, there is shown inFIG. 10 a plurality of substrates 28 a-28 h mounted upon a support plate80 (or turntable) which can be positioned within the interior of thefacility 24 for simultaneous deposition of a thin film upon each of thesubstrates 28 a-28 h. While the thin film growth process is underway,the thin film growth of a single substrate, such as the substrate 28 a,representative of the condition of each substrate, is monitored inaccordance with the process of the present invention so that informationis gathered as to the condition of the growth of the thin film on eachsubstrate in the facility 24. A thin film growth process involving aplurality of substrates is believed to be advantageous for massproduction of thin film-on-substrate structures.

Accordingly, the embodiments described herein are intended for thepurpose of illustration and not as limitation.

What is claimed is:
 1. In a process for growing or controlling thegrowth of a thin film upon the surface of a substrate involving theexposure of the substrate surface to vaporized material in a high vacuum(HV) facility, the improvement comprising: directing a beam in acomputer-controlled process toward the surface of the substrate as thesubstrate is exposed to vaporized material to effect diffraction fromthe substrate surface by the beam; monitoring the diffraction pattern ofthe substrate surface as vaporized material settles upon the substratesurface including the steps of providing a programmed andcomputer-stored target pattern of diffraction wherein the target patterncorresponds to the pattern of diffraction indicative of the desiredcondition of the film being grown upon the substrate and wherein themonitoring step is sensitive to within 0.07 of a monolayer of the filmand continually comparing the monitored pattern to the target pattern asthe vaporized material settles upon the substrate surface; andautomatically shutting off or otherwise adjusting the exposure of thesubstrate to the vaporized material when the monitored pattern matchesthe target pattern.
 2. The improvement as defined in claim 1 wherein thestep of directing is followed by a step altering, as necessary, theorientation of the surface of the substrate relative to the beam toobtain a desired crystallographic orientation of the film being grownrelative to the directed beam.
 3. The improvement as defined in claim 2wherein the step of directing is performed by an electron gun whichdirects an electron beam toward the target, and the step of alteringincludes a step of moving the substrate and electron gun relative to oneanother to adjust the crystallographic orientation of the film beinggrown upon the substrate surface relative to the directed electron beam.4. The improvement as defined in claim 3 wherein the step of movingincludes the step of moving the substrate while the electron gun remainsfixed in position.
 5. The improvement as defined in claim 4 wherein thestep of moving the substrate includes a step of rotating the substrateabout an axis to adjust the angular orientation of the surface of thesubstrate relative to the electron beam.
 6. The improvement as definedin claim 2 wherein the step of directing is performed by an x-ray gunwhich directs an x-ray beam toward the target, and the step of alteringincludes a step of moving the substrate and x-ray gun relative to oneanother to adjust the crystallographic orientation of the film beinggrown upon the substrate surface relative to the directed x-ray beam. 7.The improvement as defined in claim 6 wherein the step of movingincludes the step of moving the substrate while the x-ray gun remainsfixed in position.
 8. The improvement as defined in claim 7 wherein thestep of moving the substrate includes a step of rotating the substrateabout an axis to adjust the angular orientation of the surface of thesubstrate relative to the x-ray beam.
 9. The improvement as defined inclaim 1 wherein the beam which is directed toward the target in thedirecting step is an electron beam.
 10. The improvement as defined inclaim 1 wherein the step of shutting off or otherwise adjusting theexposure is effected when the monitored pattern achieves a conditionindicative of the desired condition of a first growth phase of the thinfilm being grown upon the substrate, and the step of shutting off orotherwise adjusting the exposure is followed by the steps of: exposingthe substrate surface to additional vaporized materials in the HVfacility to build upon the thin film grown upon the substrate during thefirst growth phase; directing a beam generally toward the surface of thesubstrate as the substrate is exposed to the additional vaporizedmaterial to effect diffraction from the thin film being built upon thesubstrate surface; monitoring the pattern of diffraction from the thinfilm as the additional vaporized material settles upon the substrate;and shutting off or otherwise adjusting the exposure of the substrate tothe additional vaporized materials when the monitored pattern achieves adesired condition indicative of the desired condition of a subsequentphase of the thin film being grown upon the substrate.
 11. Theimprovement as defined in claim 1 wherein the beam being directed towardthe target in the directing step is an x-ray beam.
 12. A process forcontrolling the growth of a thin film upon the surface of a substrateinvolving the exposure of the substrate surface to vaporized material ina high vacuum (HV) facility in multiple growth stages, the processincluding the steps of: (a) exposing the surface of the substrate tovaporized material during one growth stage of the build up of the thinfilm upon the substrate surface; (b) directing an electron beam in acomputer-controlled process toward the surface of the substrate as thesubstrate surface is exposed to the vaporized material so that electronsare diffracted from the substrate surface; (c) monitoring the pattern ofelectrons diffracted from the substrate surface as the vaporizedmaterial settles upon the substrate surface including the steps ofproviding a programmed and computer-stored target pattern of diffractionwherein the target pattern corresponds to the pattern of diffractionindicative of the desired condition of one stage of the thin film beinggrown upon the substrate and wherein the monitoring step is sensitive towithin 0.07 of a monolayer of the film and continually comparing themonitored pattern to the target pattern as the vaporized materialsettles upon the substrate surface; (d) automatically shutting off orotherwise adjusting the exposure of the substrate to the vaporizedmaterial when the monitored pattern matches the target patternindicative of the desired condition of said one stage of the thin filmbeing grown upon the substrate; and (e) repeating steps (a) through (d)during another growth stage of the build up of the thin film upon thesubstrate surface and so that the exposure of the substrate to thevaporized materials in the repeated step (d) is shut off or otherwiseadjusted when the monitored pattern achieves a programmed andcomputer-stored target pattern indicative of the desired condition ofsaid another growth stage of the thin film being grown upon thesubstrate.
 13. In a process for growing or controlling the growth of athin film of an alkaline earth oxide upon the surface of asemiconductor-based substrate involving the exposure of a surface of thesemiconductor-based substrate to atoms of alkaline earth metal andoxygen in a high vacuum environment, the improvement comprising thesteps of: exposing the surface of the semiconductor-based substrate toatoms of the alkaline earth metal following the development of highvacuum conditions about the semiconductor-based substrate but before thesurface of the semiconductor-based substrate is exposed to both alkalineearth metal atoms and oxygen atoms so that only atoms of the alkalineearth metal come to rest upon the surface of the substrate; directing abeam in a computer-controlled process toward the surface of thesubstrate as the substrate is exposed to the atoms of the alkaline earthmetal to effect diffraction from the substrate surface by the beam;monitoring the diffraction pattern of the substrate surface as the atomsof the alkaline earth metal settle upon the substrate surface includingthe steps of providing a programmed and computer-stored target patternof diffraction wherein the target pattern corresponds to the pattern ofdiffraction indicative of a preselected fraction of a monolayer of thealkaline earth metal being grown and wherein the monitoring step issensitive to within 0.07 of a monolayer of the film and continuallycomparing the monitored pattern to the target pattern as the atoms ofthe alkaline earth metal settles upon the substrate surface;automatically shutting off the exposure of the substrate to the atoms ofalkaline earth metal when the monitored pattern matches the targetpattern.
 14. The improvement as defined in claim 13 wherein thepreselected fraction of a monolayer in the step of shutting off isone-fourth of a monolayer of alkaline earth metal.
 15. In a process forgrowing or controlling the growth of a thin film whose structure isdesignated as A′BO₃ upon one of an AO or a BO₃ truncated perovskitesurface wherein each unit cell of the A′BO₃ structure is comprised of asingle plane of alkaline earth oxide (AeO) and a single plane of atransition metal oxide (TmO) and wherein the growth process involves theexposure of an AO or a BO₂ truncated perovskite surface alternatively toatoms of the AeO plane and to atoms of the TmO plane during the build-upof the thin film one single plane layer-at-a-time in a high vacuumenvironment, the improvement comprising the steps of: directing a beamin a computer-controlled process toward the AO or BO₂ truncatedperovskite surface as the AO or BO₂ truncated surface is exposed toeither the atoms of the Aeo plane or the atoms of the TmO plane toeffect diffraction from the AO or BO₂ surface by the beam; monitoringthe diffraction pattern of the AO surface as the corresponding atomssettle upon the AO surface in a build-up process including the steps ofproviding a programmed and computer-stored target pattern of diffractionwherein the target pattern corresponds to the pattern of diffractionindicative of the desired condition of the film being grown and whereinthe monitoring step is sensitive to within 0.07 of a monolayer andcontinually comparing the monitored pattern to the target pattern as thevaporized material settles upon the substrate surface; and automaticallyhalting or adjusting the deposition process when the monitored patternmatches the target pattern.
 16. The improvement as defined in claim 15wherein the adjusting step includes a shutting off of the exposure ofthe AO or BO₂ truncated surface to atoms being deposited thereon whenthe monitored pattern achieves a condition indicative that a singleplane layer of the AeO plane or the TmO plane has been deposited uponthe AO or BO₂ truncated surface.
 17. The improvement as defined in claim14 wherein the directing step directs the beam toward the AO or BO₂truncated surface in a <210> direction.